Hi Mirek,

Sorry for the alarm. This is likely my own fault in one way or another:

While attempting to create a testcase, I discovered that my complex polyline optimization routines might end up skipping the stroking of polylines, e.g. if the lines are too narrow to display at specific zoom levels. This in turn leaves the entered vertices (Move()/Line()) in the Painter unused and probably cause trouble afterwards in the MT optimized code while it is fine with ST code. I was able to fix the MT rendering symptoms by simply enclosing the my polyline code within a Begin()/End() pair in the BufferPainter.

Thanks and have a nice 2018!

Best regards,

Tom